Which of the following metal can be extracted by reduction with carbon and heating alone in the air?

Low-reactive metals like mercury and copper can be extracted by reduction with carbon and heating alone in the air.

(i) Reduction of its ore with carbon-

$2\mathrm{CuO} + \mathrm{C}\to 2\mathrm{Cu} + {\mathrm{CO}}_2$

(ii) Heating alone in the air-

${\text{2Cu}}_{\text{2}}{\text{S + 3O}}_{\text{2 }}\stackrel{∆}{\to }{\text{2Cu}}_2{\text{O + 2SO}}_2$